The invention relates to a fusible link construction of the kind especially adapted for use in conditioning, for automatic operation in the event of a fire, the release of a locking mechanism, the closing of a fire door, the release of a sprinkler operating lever, and the like. Conventionally, such mechanisms have a weight or spring biased actuator maintained in a non-operating position against the bias of the weight or spring by means of a so-called fusible link, which, in response to the increase to a predetermined level of the ambient temperature, separates and enables the bias imposed on the operator to move the latter from its non-operating position to its operating position.
Various kinds of fusible links have been proposed heretofore, one of the most common of which comprises a pair of flat bodies arranged side by side and separably bonded to one another by a thermally sensitive substance which liquifies when its temperature is raised to a predetermined level, thereby destroying the bond between the links and permitting them to separate.
Another fusible link of the general class to which the invention relates is that disclosed in U.S. Pat. No. 3,779,004 granted Dec. 18, 1973. This construction employs a first link having an opening therein and a second link having a loop portion that is accommodated in the opening of the first link. Fitted into the loop is a strut which normally is of such length as to span the opening and prevent withdrawal of the loop from the opening.
One of the disadvantages of the side-by-side links bonded to one another is that the thermally sensitive bonding material has a tendency to creep over a period of time, particularly if it is subject to tensile or compressive forces. In time, therefore, the bonding material may creep to an extent such that it is incapable of maintaining the plates in joined condition or permits shortening or elongation of the assembly to the point that proper operation of the mechanism whose operation is to be controlled cannot be ensured. A disadvantage of the second known fusible link construction referred to above, aside from the multiplicity of parts of which it is constructed, is the difficulty of assembling such parts, as well as combatting the tendency of the thermally sensitive material to creep or cold flow.
One of the objects of the present invention, therefore, is to provide a fusible link construction which overcomes the disadvantages of known constructions adapted for similar purposes.